1. Field of the Invention
This invention is concerned with improving the flow properties and pour point characteristics of hydrocarbon oils. More particularly, this invention is concerned with low-pour hydrocarbon oil compositions comprising a hydrocarbon oil such as a middle distillate, a gas oil, a residual fuel oil, crude oil, etc. and an effective pour-depressant amount of an oil-soluble, alkylated polybenzyl polymer or copolymer.
2. Description of the Prior Art
As is well known, many hydrocarbon oils contain quantities of wax which render them viscous and give unacceptably high pour points. These oils behave as non-Newtonian liquids at low temperatures: exhibit variable solidifying temperature and peculiar hysteresis phenomena all of which render them difficult to use as fuel.
One approach used in converting these oils has been to subject them to fairly lengthy dewaxing procedures. This, however, is an expensive process.
Another approach which has been used to bring the viscosity of the waxy hydrocarbon oils to suitable levels has been to dilute or "cut" them with a major amount of lighter distillate oils but this also is an expensive procedure because of the considerably higher costs of the distillate oils relative to the higher boiling oils.
A number of additives have been suggested and tried with success in lubricating oils, middle distillates, gas oils, etc. in order to tie in the wax therein and improve flow at low temperatures. Such additives consist either of compounds such as alkylated polystyrene, etc. or of copolymer of ethylene-vinyl saturated aliphatic monocarboxylic acid esters of a molecular weight up to 3000 and containing from 15 to 25 percent by weight of the vinyl saturated aliphatic monocarboxylic acid ester. These known additives are not, however, effective in depressing the pour point of certain hydrocarbon oil compositions.
In recent years the restrictive specifications limiting the sulfur content of fuel oils including those containing a major amount of gas oils has made the manufacture of such fuels a much more difficult task than previously. In many localities, low-sulfur, high-pour fuels are being substituted for previously utilized high-sulfur low-pour fuels. In order to meet the stringent pour point specifications of such fuel oils pour depressants are being used. A particular effective class of pour depressants are the ethylene-vinyl acetate copolymers having molecular weights ranging from about 15,000 to about 60,000 and having an ethylene content of about 45 to about 90 percent. Although the ethylene-vinyl acetate copolymers have been shown to be effective in reducing the pour points of crudes and fuel oil blends containing distillate they have not been found to be very effective in reducing the pour points of certain other hydrocarbon oils such as vacuum gas oils, etc.
It is therefore the main object of the present invention to provide low pour hydrocarbon oil compositions based on middle distillates, gas oils, residual fuel, crude oils, etc. and containing an effective pour depressant amount of an alkylated polybenzyl polymer or copolymer.